I think problem with realism will come. In fact it should be like 2000t+ of water out of 1 rock. However, when it's applied to current mechanic (laser/pieces/refine) you can't do 120% chunk.decreasing the rarity of the lower ones.
P.S. actually it's pretty dumb right now "rock has 20% of water", okey ...but what contains water then ? After mining such basic things like water/oxygen it must remain nothing.
I can understand 20% and 80% of water in rock. But not 20% of water and 80% "trash", because we mine all sorts of "trash" elsewhere.
...so to proper balance, they should start from very deep change, i.e. when rock 100% mined it's gone. If you mine water - rock of ship size, you get at least ship weight amount of water.